What is respiratory syncytial virus?

Respiratory syncytial virus is a common cause of respiratory illness in babies and young children—most kids get it before age 2—but it can affect people of any age. RSV typically circulates during the fall, winter and early spring, causing annual outbreaks. It usually causes cold-like symptoms, but infants and older people are at greater risk for serious illness. RSV is the leading cause of infant hospitalization in the U.S., according to the Centers for Disease Control and Prevention (CDC).

How does RSV spread?

RSV is typically transmitted via contact with saliva, nasal discharge or respiratory droplets. The virus can survive on surfaces for several hours. Most people with RSV are contagious for about a week, though the duration may be longer in infants and immunocompromised people. Hand washing, covering your mouth and nose when you sneeze or cough, cleaning surfaces and objects and avoiding crowds can reduce the spread of RSV. People who are sick should stay home from school or work. Some experts recommend wearing face masks, but their effectiveness is not clear, and this can be difficult for young children and is not advised for infants. RSV does not confer long-lasting immunity, and people can get the virus more than once.

What are the symptoms of RSV?

RSV typically causes a cold-like illness, but it can sometimes cause more severe lower respiratory infections. Symptoms may include a runny or stuffy nose, sore throat, cough, sneezing, wheezing (particularly in children), loss of appetite, fever, headache and irritability or decreased activity in infants. However, symptoms may be subtle in babies, and most adults with RSV have mild or no symptoms. People with more severe cases may develop pneumonia (lung inflammation), and children may develop bronchiolitis (inflammation and narrowing of small breathing passages).


What are the risk factors for severe RSV?

Severe RSV respiratory illness occurs most often in infants younger than 6 months; around 2% of babies in this age group may require hospitalization, according to the CDC. Premature infants, immunocompromised children and children with chronic lung disease, congenital heart disease or neuromuscular disorders are considered at high risk. Exposure to second-hand smoke is also a risk factor, while breastfeeding is protective. Among adults, those over age 65 and those with compromised immunity or underlying conditions, such as chronic lung or heart disease, are at greatest risk.


How is RSV diagnosed?

The symptoms of RSV resemble those of other respiratory illnesses, including colds, flu and COVID-19. Testing is the only sure way to diagnose RSV. PCR or antigen tests may be done using fluid samples from the upper or lower respiratory tract. Antigen tests are highly sensitive for infants and young children but less so for older children and adults. In some cases, a chest X-ray may be done to look for lung involvement.


How is RSV treated?
Most healthy infants, children and adults with RSV will have mild to moderate illness, and symptoms can be managed at home with supportive care. Over-the-counter medications may be used to relieve pain, fever and congestion. Drink plenty of fluids and keep the air moist with a humidifier. Most children and adults recover in about a week.

Infants and young children who are at risk for severe illness may receive preventive therapy using the monoclonal antibodies palivizumab (Synagis) or nirsevimab (Beyfortus). There are currently no antiviral medications specifically approved for RSV—though ribavirin is sometimes used in severe cases—and antibiotics are not effective against viruses. Children and adults with severe disease may require hospitalization, and some will need oxygen therapy or mechanical ventilation.

Is there a vaccine for RSV?

The Food and Drug Administration (FDA) approved the first two RSV vaccinesGSK’s Arexvy and Pfizer’s Abrysvo, in May 2023. The CDC recommends that adults ages 60 and older discuss vaccination with their health care providers. The vaccines are generally safe and well tolerated. The FDA also approved Abrysvo for pregnant women to prevent respiratory illness in their infants.

RSV vaccines are not approved for children but vaccinating women during late pregnancy protects their infants. The CDC recommends Abrysvo as a seasonal vaccine for people between 32 and 36 weeks of pregnancy. In addition, the CDC recommends a newly approved monoclonal antibody immunization, Beyfortus (nirsevimab), for infants under 8 months of age to prevent RSV respiratory illness.

Last Reviewed: September 23, 2023